2. Asteroids, Meteors and Meteoroids

3. Asteroids Name meaning “star-like bodies” AKA “minor planets” or “planetoids” Move along a very eccentric path Mostly located in the asteroid belt

4. Asteroids Number of asteroids is more than 500,000 Three Biggest: Ceres, Pallas and Vesta Two types – S-type (silicate or rocky material) Reflective More in the inner part of the asteroid belt – C-type (or carbonaceous) These tend to be darker and not very reflective More in the outer part of the asteroid belt

5. Earth-Crossing Asteroids Have HIGHLY elliptical orbits AKA “Apollo Asteroids” On average, during any given million-year period, our planet is struck by about three asteroids.

6. What happens if an asteroid was going to crash into the Earth? http://www.youtube.com/watch?v=Agdvt9M3N JA

7. Trojan Asteroids Orbits at the distance of Jupiter Locked into orbit – always stay in the same position relative to the planet

8. Is It A Meteor, Meteoroid, Meteorite? Starts as a Meteoroid – chunk of interplanetary stuff that enters the Earth’s atmosphere Becomes a Meteor – the bright steak in the sky known as a “shooting star” from a meteoroid entering the Earth’s atmosphere as it heats up And then maybe a Meteorite – Any piece of a meteoroid that survives and lands on Earth

9. Meteoroids Meteoroids are a lot smaller – 100m or less in size Meteor Showers occur when Earth passes through a comet’s orbit – As a comet approaches the sun, some chunks get pulled off and follow the comet – Chunks are called a meteoroid swarm

10. Impact Craters Floor - Bowl shaped or flat, characteristically below surrounding ground level unless filled in with lava. Ejecta- Material surrounding the crater that was excavated during the impact event. Ejecta becomes thinner away from the crater. Raised Rim - Rock thrown out of the crater and deposited as a ring-shaped pile of debris at the crater's edge during the explosion and excavation of an impact event. Walls - Characteristically steep and may have giant stairs called terraces. Rays - Bright streaks starting from a crater and extending away for great distances. Central Uplifts - Mountains formed because of the huge increase and rapid decrease in pressure during the impact event. They occur only in the center of craters that are larger than 40 km diameter. Impactors – A projectile that crashes into the surface of another object. It is typically referred to as a meteorite. Velocity – The rate of speed of an object moving in a specific direction. Typical characteristics of an impact crater are labeled on this photograph of